1. Field of the Invention
This invention relates to fuzzy logic, and more particularly to methods for storing membership functions, as well as processors of the fuzzy type for implementing the method.
2. Discussion of the Related Art
A survey of both theoretical and practical aspects of fuzzy logic processing is to be found in M. M. Gupta and T. Yamakawa, "FUZZY COMPUTING", North-Holland, 1988.
One of the most critical aspects in the design of architectures for fuzzy logic processing is he representation of the linguistic terms that collectively form the so-called dictionary of terms, which is in practice the equivalent of representing the functions of membership to such terms.
The techniques for representing membership functions can be divided into two general classes: those which take no account of the function shape, and usually provide for function sampling, and those which only apply to particular shapes, such as triangular, trapezoidal, and other shapes of the functions.
Some methods of storing membership functions from the former class are described in Patent Applications EP 628 902 and EP 628 903, wherein only the respective non-null samples of each function are stored.
A method of storing membership functions from the latter class is described in Patent Application EP 675 431, wherein an apex and the slopes on the left-hand and right-hand sides of the apex are stored for each function. A circuit for computing such functions, starting from their storing in the manner outlined above, is described in Patent Application EP 675 430.
It will be appreciated from the foregoing concise review of prior methods that considerable work has been devoted to minimizing the storage capacity requirements for each individual membership function.